Re: [Qemu-devel] [PATCH 03/22] qapi: add Error object

[Stefan Hajnoczi]

On Mon, Mar 7, 2011 at 1:36 PM, Anthony Liguori <address@hidden> wrote:
> On 03/07/2011 05:38 AM, Stefan Hajnoczi wrote:
>>
>> On Mon, Mar 7, 2011 at 1:22 AM, Anthony Liguori<address@hidden>
>>  wrote:
>>
>>>
>>> +struct Error
>>> +{
>>> +    QDict *obj;
>>> +    const char *fmt;
>>> +    char *msg;
>>> +};
>>>
>>
>> I wonder why fmt is const char * but msg is char *.  Users should use
>> error_get_pretty() instead of accessing msg directly and that function
>> returns const char * so it seems that msg should be const char * to
>> start with.
>>
>
> fmt doesn't need to be free'd whereas msg does.  If you make msg const char
> *, the compiler will complain when you pass that to qemu_free().  I tend to
> think of the difference between 'const char *' and 'char *' as a string that
> I don't own vs. a string that I do own the reference to.
>
> It's not universally true but it tends to work nicely most of the time.

Thanks, that makes sense.

Stefan